1. Field of the Invention
The present invention relates to escape devices of elevator and more particularly to a mechanism which can cause an elevator escape device to automatically return to its normal position after passengers trapped in a malfunctioned car (e.g., due to power outage) have made a successful escape by lowering or hoisting the car to be flush with a floor by operating the escape device.
2. Description of Related Art
A conventional elevator escape device 70 is shown in FIGS. 6, 7, and 8. In a case of car failure, a drive sheave 40 is moved to a position between two opposite secondary sheaves 30 and interengaged therewith by rotating a first handle 44 by a trapped passenger to cause a lever 41 to move along an arcuate groove 64 until the lever 41 reaches a hooked portion 65 at one end of the groove 64 and is locked therein. Next, the passenger can grasp a second handle 43 to rotate a wheel 42 and thus the drive sheave 40. The rope 10 then is activated to run downward along the grooved rims of the drive sheave 40 and the secondary sheaves 30. In response, the escape device 70 is activated to lower or hoist a car 20 until the car 20 reaches a safe position for passenger(s) escape.
However, the prior art suffered from a disadvantage. For example, the lever 41 is not unlocked even after the failure has been fixed. As such, a brake of the car 20 may be still disabled after the elevator has begun a normal operation due to, for example, the restoration of power. This can cause the car 20 to lower rapidly due to the unbalanced counterweight. This is very dangerous. For solving this problem, a manual movement of the lever 41 by a maintenance technician to return to its normal position is required after the car failure has been fixed. This is inconvenient. Hence, a need for improvement exists.